Voltage regulator



w. c. HALL venues nseunnon Oi'iginal Filed Jan. 26, 1940 April 14, 1943.

2 sham-sheet v1 m H Y w r a Z a T "w m A Y I April 14, 1942. w. c. HALL VOLTAGE REGULATOR Original Filed Jan. 26, 1940 2 Sheets-Sheet 2 ukw w vs C NH 0 E d w W e u A Patented Apr. 14, 1942 1mm STATES PATENT OFFICE VOLTAGE REGULATOR.

Wayne 0. flail, Washington, D. C.

Original application January 26, 1940, Serial No. 315,722. Divided and this application November 29, 1940, Serial No. 367,719

(Granted under the act of March 8, 1883, .as

9 Claims.

amended April 30, 1928; 870 O. G. 7 57) My invention relates voltage regulator and to an apparatus for measuring mechanical power and/or torque. The present. application is a division of my application Serial No. 315,722 flied January 26, .1940; In the parent application the novel features of the power and/or torque measuring apparatus are claimed, while the claims of the'present application are limited to the novel. features'of the voltage regulator.

The regulator of the .present invention is adaptedfor use with the power and/or torque meter which includes .inccmbination with a power shaft, aspace discharge device comprising an envelope enclosing at least three electrodes at least one of which is electron emissive and at least one-of which is movable with respect to the envelope.- The envelope of the space discharge device and at least the movable electrode thereof are secured to the shaft at'spaced points therealong in such amanner as to cause an ingo the indicating instrument across one of the crease inresistance between aplurality of the p .electrodes simultaneously with a decrease in a like resistance upon, subjecting the shaft to a torsional deflection. The magnitude of this simultaneous variation in the interelectrode re-.

'cent.

that of the generator in the other bridge diagonal. Where-a qualitative indication of transmitted shaft power or torque is desired, it is not necessary to maintain the emissivity of the electron emissive electrode of the space discharge device or the voltage across the bridge diagonal that is independent of shaft speed constant. On the other hand, where a precision or quantitative indication of transmitted power or torque is desired, the electron emissivity and voltage referred to must be maintained substantially constant although if the reading of the apparatus may be permitted to be-in' error by a few percent, these quantities may be allowed to vary from the established mean value by a few per- Am substantial deviation, however, in the constancy of these quantities from predetermined values will so eflect the sensitivity of bridge diagonals asto nullify any previous calibration of the apparatus.

For maintaining a substantially constant electron emissivity and a substantially constant voltage across one diagonal of the bridge circuit when desired, I have devised a novel regusistances is, therefore, approximately propor-' tional tothe torque being transmitted by the shaft. p v

The space discharge device is connected in a bridge circuit to form two branches or arms thereof, which circuitis normally in a state of balance when no power or torque is being transmitted by the shaft. Where it is desired to measure-the mechanical power under transmission, a generator, the voltage output of which is latory system for regulating a fluctuating source of direct 'current electromotive force which, while of general application, may be advantageously utilized inthe.power and/or torque meter. This regulatory system includes a fluctuating source of direct current electromotive force connected in circuit with a plurality of parallel branches and a branch across which it proportional to the speed of the shaft, is utilized and is driven by the shaft at a speed equal to or -"-proportional to that of the shaft. This gene ratorzis'connected across a diagonal of the bridge 'circuit while an electricalv instrument for directly and continuously indicating a quantity that isproportional to both the torque and speed of the shaft is connected across the remaining brldgediagonal. The connection of the generator as aforesaid makes the provision of any further voltage sources for power measurements unnecessary and thus results in the production of a highly economical'and compact apparatus. For indicating the torque under transmission, an instrument is likewise employed in one bridge diagonal that will directly and continuously indicate a quantity which is proportional to the 1 torque of the shaft, while avoltage that is independent of the shaft speed is substituted for is desired to maintain a substantially constant voltage drop. Means responsive to any current change in one parallel branch attending any fluctuation in the direct current electromotive ,force causes a substantially equal but opposite current change in the other parallel branch, whereby the current in the remaining circuit branch and hence the voltage drop thereacross tory system of general application for use with a power and/or torque meter to insure quantitative or precision indications of the transmitted shaft power or torque.

Other objects and many of the attendant advantages of this invention will be readily appreciated as-the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying sheets of drawings wherein:

Fig. 1 discloses the preferred embodiment of the apparatus of my invention for measuring transmitted shaft power and/or torque, showing, among other things, .the space discharge device associated with the power shaft connected in the bridge circuit for forming two branches thereof together with the novel regulatory system;

Fig. 2 is an enlarged sectional view taken on the line 2-2 of Fig. 1 showing in greater detail, among other things, the construction employed for maintainingia concentric relationship between the shaft encircling sleeves that engage the space discharge device;

; Fig. 3 is the current-voltage characteristic of the ballast tube which is included in one of the parallel branches of the regulatory system showing how the current in this branch varies in response to any change in the fluctuating source of direct current electromotive force; and

Fig. 4 is the current-voltage characteristic of that branch of the regulatory system-across which it is desired to maintain a substantially constant voltage drop showing how the current in this branch varies in response to any change in the bridge diagonals, as well as a function of the emissivity of the cathode of the space discharge device associated with the power shaft.

Turning now to Figs. 1 and 2 of the drawings, there is shown depicted therein a rotatable shaft 1 having securely clamped thereto at spaced points 2 and 3 the sectionalized sleeves 4 and 5, one of which exceeds the other in length. The set screws 6 and 1 are employed at the respective points of securement of sleeves 4 and 5 to the shaft to make certain that no peripheral or longitudinal movement of the sleeves relative to the shaft will occur. is supported from and maintained concentric withthe sleeve 5 by means of the tension members 8 constructed as thin flexible plates which fluctuating source of direct current electromotive force.

Before proceeding to a detailed description of the preferred embodiment 01' my invention it is desired, among other thin88, to make certain general remarks regarding the space discharge device associated with .the'power shaft. so as to insure clarity in the subsequent exposition. As

noted hereinbeifore, this space discharge device comprises an envelope enclosing at least three electrodes, at least one of which is electron emissive to thus serve as a cathode and at least one of which is movable with respect to the envelope.

While a cursory examination of Fig. .1 of the drawings shows the cathode of the space discharge device associated with the power shaft as of the thermionic type, it is to be understood that other types of cathodes may be employed.

The envelope of this space discharge device, which is fashioned from any of the materials known to the prior art and serves to enclose the electrodes, may be evacuated to produce a high vacuum and thus insure a substantially pure electron discharge or may alternatively be provided with a suitable filling of a gas or vapor, gases .or vapors, or mixtures of gases and vapors at a selected pressure or pressures to insure the desired operating characteristics.

Finally, and of great importance, it is essential that the meaning ofthe term "sensitivity" be understood as used with respect to the electrical indicating instrument connected across one of the bridge diagonals. As here employed, the

term sensitivity designates the indication or incremental change in-the reading of the instrument per unit deflection of the movable electrode of the space discharge device. The sensitivity of the indicating instrument is a function of theelectromotive force impressed across one of the movement between the sleeves.

offer no appreciable obstruction to rotational These tension members are secured .to the terminal portions of the sleeves in ;any.suitable manner. It is thus evident that any angular or torsional deflection of the shaft'intermediate the points of securement of the sleeves thereto upon the application of any torque will be transmitted to the flanges 9 and II of the respective sleeves 4 and 5 and cause them to be angularly displaced relative to each other by the same amount.

A space discharge device identified in general by the reference character II is shown, by way of example, as comprising an envelope l2 enclosing a thermionic cathode I3 stationarily mounted with respect to the envelope and interposed between a pair of conjointly movable anodes l4 and IS, the" three electrodes being mounted for simultaneous cooperation and being disposed to cause an'increase in one anode-cathode resistance simultaneously with a decrease in a like re sistance. The two anodes .I4 and I! are rigidly secured to the elongated member or arm I6 and are electrically insulated from each other and from the arm in any suitable manner. The arm. as shown, extends from the envelopeinterior to a point exteriorly thereof and at its point of emergence is flexibly and hermetically sealed to the envelope by-employment of any of the well-understood expedients known to the prior art.

The envelope ll of the space discharge device is suitably mounted on the flange IQ of the sleeve 5, while the deflector arm l6 adjacent its outer extremity is laterally engaged by a series of set screws I! (Fig. 2) supported by a bracket I8 secured to the flange 9 of the sleeve 4. Thus, it should be clear that any relative movement of the flanges 9 and III attending any angular or torsional deflection of the shaft will cause simultaneously a decrease in spacing between the first anode and the cathode and an increase in spacing between the second anode and cathode, the variation in spacing being directly proportional to the torque under transmission. In consequence of the foregoing, there will be produced an increase in one interelectrode resistance simultaneously with a decrease in a like resistance.

The space discharge device H is connected in a bridge circuit to form two branches or arms thereof, the remaining two branches being constituted by the two fixed resistors l9 and 20 and so much of the variable balancing resistor II as may be included therein byappropriate adjustment of the sliding contact 22. It is thus evident that the bridge may be initially balanced prior to any measuring operation by suitable manipulation of the sliding contact 22 associated with the balancing resistor 2|. The variable resistor The free end of the sleeve 4 23 under the control of the sliding contact 24 is connected to the switch 25 by means of which the desired electromotive force is impressed across one of the brid'gediagonals. By varying the resistor 23, it is possible to vary slightly the voltage impressed across the bridge diagonal 26-21 one end of which, for convenience is grounded; and hence to vary the sensitivity of the electrical instrument or meter 23, which resistor 45 so that the fraction of the voltage thereof subsequently impressed across the bridge circuit may at no time be excessive. Where the voltage developed by the generator at the maximum speed of the power shaft is within the desired operating range, the voltage dropping reand anode l5, cathode II with the resistors l9 and 2-3 and so much of the vari-.

able resistor 2| that may be respectivelyassociated therewith constituting the remaining two.

branches.

Since only the space discharge device ii is secured to and rotates with the shaft provision must be made for electrically connecting the same with the resistors l3 and 23 included in two o'fthe branches of the bridge circuit and with suitable sources of electromotive force for energizing the bridge circuit and the thermionic cathode ll of the space discharge device. To this end slip rings 33, 3|, 32 and 33 are insulatingly mounted from each other and from the shaft to rotate with the latter and cooperate respectively with brushes 30, 3|, 32 and 33. By

mearis of this arrangement, a continuous electrical connection is provided between anodes l4,

- I5 and the respective resistors I3, 23 through conductors 34,35 interconnecting anodes I4, l5

and slip rings 32, 33; and conductors 34, 35' interconnecting the brushes 32', 33' with the terminal portions 25', 21' of the respective resistors I9, 20. The thermionic cathode I3 is maintained in continuous electrical connection with a suitable source of electromotive force which is preferably, although not necessarily, supplied by the regulatory system to be described more in detail hereinafter. This interconnection is achieved by means of conductors 33' connecting the cathode and the slip rings 30 and 3|; and the conductors 36' interconnecting the brushes 33' and 3| with the current mains 31 and 33 leading to the regulatory system. As connected, the cathode II is energized by a substantially constant current to insure a substantially constant electron emissivity.

' A direct current generator 33, the voltageoutput of which is proportional to the shaft speed, is driven by the shaft I through a gear 43 rigidly secured thereto which is in meshing engagement with a pinion 4| securely mounted on the armature shaft. Thus, the electromotive force developed at the generator terminals 42 is directly proportional to the speed of the rotating power shaft which latter quantity may, if desired, be directly indicated by the standard type of voltmeter 43 calibrated in units of speed and associated with the double-pole double-throw switch 44 connected to the generator terminals 42 by means of the conductors 45.

The voltage developed at the generator terminals 42 is impressed upon the voltage dropping sistor 45 may be dispensed with. The sensitivity of the indicating instrument 28 connected across the bridge diagonal 2521' is a linear function of the voltage impressed across the bridge diagonal 26-21 only so long as this voltage does not cause near saturation current to flow in the space discharge device associated with the power shaft I. To prevent a voltage in excess of this critical saturation voltage from being impressed across the bridge diagonal 2621 at maximum shaft speed with the generator here employed, the dropping resistor 45 is utilized. This resistor insures. that only the proper fraction of the electromotive force at maximum shaft speed is made available for subsequent application to the bridge circuit.

A conductor 41 connects a suitable point along the length of the dropping resistor 43, which is always maintained at a positive potential by the reversing switch 44, with the power contact 43 of the switch 25. The point of the dropping resistor 45 which is always maintained at fl negative potential, as indicated, i connected by means of the conductor 43 to thecurrent main 33 which' is grounded at 21. A switch 53, when closed, es-

. tablishes electrical continuity along the length of the conductor 41 and may, if desired, be interlocked with the single-throw double-pole switch 5|. The function of this latter switch, as will be pointedoutmore'in detailhereinafter, is to 'make possible the measurement of the saturation current of the space discharge device associated with the power shaft when this is desired. These interlocking switches and 5| are so arranged that when one is closed the other is open and vice versa. Normally, the single-pole singlethrow switch 53 remains closed and the doublepole switch 5| -in' consequence thereof open.

, Thus, it should be clear that with the switch 50 closed and the switch 25thrown to engage the power contact 43 that a fixed fraction of the variable electromotive force of the generator 39 will be impressed across the bridge diagonal 23-21 and that the apparatus as connected may now be" employed for the measurement of transmitted shaft power.

By throwing the switch 25 from its position of engagement with the power contact 43 to a position of engagement with the torque contact 52,

the apparatus is forthwith changed from a power measuring instrumentality to a device for measuring torque. Engagement of the switch 25 with the torque contact 52 has the effect of disconnecting the variable generator voltage from the bridge circuit and of substituting therefor a voltage which may or may not have a substantially constant value but whose value in any event is definitely independent of the shaft speed. In the preferred embodiment of the torque meter, the emissivity of the-cathode l3 of the space discharge device II and the voltage impressed across the bridge diagonal 25-21 are maintained substantially constant. The connection of the cathode i3 is the same as that already described when using the apparatus for the measurement of power and may be such as to provide either a variable or a substantially constant electron emissivity.

The engagement of the switch 25 with the torque contact 52 has the effect of connecting the branch 53-21 of the regulatory system, across which there is maintained a substantially constant voltage drop, to the bridge circuit. Thus, there is maintained across the. bridge diagonal 28-21 a substantially constant electromotive force. The foregoing is made possible by virtue of the conductor 54 which connects the upper point or point of positive polarity 53 of the aforesaid regulatory branch with the torque contact 52, a current meter 55 being in circuit with the conductor for a reason to be pointed out presently. The same meter 28 connected across the bridge diagonal 252|' may, if desired, be employed for indicating a quantity that i proportional to the torque under transmission.

In the preferred embodiment of my apparatus for the measurement of power and/or torque, it is desired to maintain the emissivity of the thermionic cathode I3 of the space discharge device II substantially constant. The electron emissivity of the cathode is a function of its surface condition and of its operating temperature. The temperature of the cathode is maintained at an initial and desired value by energizing the same with a substantially constant current furnished by the regulatory system. It may happen, however, that the surface condition of the thermionic cathode becomes impaired during the operating life of the space discharge device thus necessitating a slight increase or decrease in temperature of the cathode to restore the initial and desired value of electron emissivity. This is accomin engagement therewith. By periodically checking the saturation current of the space discharge device H in the manner described above and by maintaining this current at all times substan tially constant, a substantially constant electron emissivity is insured.

For maintaining a substantially constant electron emissivity and a substantially constant voltage across one 01' the diagonals of the bridge circuit when desired, I have devised a novel regulatory system for regulating a fluctuating source of direct current electromotive force which, while of general application, may be advantageously utilized in the apparatus of the present invention. This regulatory system includes a fluctuating source of direct current electromotive force connected in circuit with a plurality of parallel branches and a branch across which there is maintained a substantially constant voltage drop by the regulatory action of the system. Means responsive to any current change in one parallel branch attending any fluctuation in the direct current electromotive force causes a substantially equal but opposite current change in the other parallel branch, whereby the current in the remaining circuit branch and hence the voltage drop thereacross is maintained substantially'constant. By connecting the electron emissive electrode of the space discharge device in the latter or remaining circuit branch it will be energized by a substantially constant current at all times,

plished by energizing the cathode with a slightly higher or lower current, this new current value, however, being llkewise maintained substantially constant by the regulatory system. To this end provision i made for checking the emissivity of the cathode and for restoring the same to its initial value of emissivity when this becomes nec-' essary.

Switch 5!, which is electrically connected to conductor 54 by the conductor 58, when closed connects the substantially constant source of electromotive force of the branch 53-41 of the regulatory system directly across the space discharge device, thus causing saturation current to flow which is a direct measurement of the emissivity of the cathode IS. The circuit thus completed by closure of the switch 5| extends from the junction 53 of the regulatory system through the conductor 54, meter 55 (which may be a milliammeter) and switch 5| 'to the brushes 32, 33' by virtue of the conductors 34', 35' connected respectively therewith. aforesaid continues from the slip rings 32, 33 to their respective anodes I4, l5 through the conductors 34, 35 and from thence through the oathode I3, slip ring 30, brush 30' and conductor 36 to the remaining terminal 21 of the regulatory branch. Thus, it should be clear that when the check switch 5! is closed the effect is to short circuit the bridge resistors I! and 20 and to cause the sum of the two plate currents of the space discharge device H or the saturation currents thereof to flow through the milliammeter 55.

Any change in the emissivity of the thermionic cathode i3 attending any change in its surface condition may be compensated for by causing a slight variation in current through the cathode, the new current value, however, being maintained substantially constant by the regulatory system. This is accomplished by suitably adjusting a variable resistor 51 in parallel with the cathode l3 through the sliding contact 5| The circuit closcd as thus maintaining its emissivity substantially constant. This latter circuit branch may also provide a substantially constant source of electromotive force for one diagonal of the bridge circuit when employing the apparatus for the measurement of torque as has already been noted at length hereinbefore.

hydrogen in which there is enclosed a ballast resistor 52 fabricated of iron wire connectible with the positive terminal of the fluctuating source of direct current electromotive force by closure of the switch 63.

The current voltage characteristic of the ballast tube 59 depicted in Fig. 3 of the drawings shows how the total turrent I1 in the parallel branch described in the preceding paragraph varies in response to any voltage change in the fluctuating source of direct current electromotive force. It will be noted that within a limited range of voltage variation of the direct current source of electromotive force, that the current variation in the parallel branch is substantially linearly related to the varying voltage drop across the ballast tube and that this substantially linear current variation is from Iv to I1" where 11, for convenience of exposition, may be taken as the quiescent value of current about which-the current fluctuations or incremental current changes A I1 occur. Such a large current variation is not permissible where precision measurements are to be made with the power and/or torque meter since, among other things, wide changes in electron emissivity would ensue.

The second of theparallel branches includes one or more shunt connected tubes or space dis-' with its variable resistor 51.

charge devices which operate essentially as triodes. I have shown, by way of example, four RCA Type-48 tubes identified in general by the reference character 64 in which the screen grids are tied back to their respective anodes in each instance so that the tubes may operate as triodes. While any conventional prior art triode may be employed, this type of tube was chosen because of its ability to deliver large power at relatively low plate voltages.

Thescreen grids 65 tied to the anodes 66 are connected in shunt and to a terminal 61 of the first parallel branch by means of the conductor 68; while the indirectly heated cathodes 69 energized by the heater elements are likewise shunt connected and by the conductor 1! are electrically connected to the remaining terminal 53 of the first parallel branch. The control grids 12 of the tubes 6! are also connected in 'shunt and have their grid circuits completed in a manner to be described more in detail hereinafter. v 7

It is to be emphasized that the triodes 64 must at all times be operated substantially onthe linear portions of their ire characteristic and that the control grids 12 must never swing positive with respect to their cathodes 6! so as to prevent any disturbance in the voltage relationships of the system. From the foregoing, it follows that any current change in the second of the parallel branches will be linearly related to any voltage change on the control grids 12 andv that this branch current may by suitable adjustment have the desired compensating effect 7 on the linearly varying current of the first parallel branch.

Thus, the number of tubes in the second parallel branch need only be sufficient to carry a current slightly in excess of the difference between the maximum and minimum linear currents of the difference between 1 and 11' of the first parallel branch. The tubes N must of necessity be capable of carrying a slight excess current since otherwise they would be operating on a non-linear portion of the Hg characteristic at zero plate current which is not permissible if the conditions above noted are to be met.

, Therefore, even when the ballast tube is passing its maximum current a small current is passing through each of the tubes 84. The total quies cent current in the second parallel branch flowing toward the junction point 53 is designated I: and corresponds to the similarly flowing quiescent current I1 of the first parallel branch.

The circuit branch across wlflch it is desired to maintain a substantially constant voltage drop and hence a constant current flow therethrough extends from the junction point 53 to the grounded point 21. This latter Junction point, i will be observed, is connected to the negative terminal of the fluctuating source of direct current velectromotive force by the conductor 13. Thus, it should be clear that in the regulatory system of the present invention a fluctuating source of direct current eiectromotive force is connected in circuit with a plurality of parallel branches and a branch across which a substantially constant voltage drop is to be maintained.

This constant current, constant voltage branch 53-21 includes, by way of example, the resistors 14, 15, 16 and the filament resistor I! in shunt The resistors 14 and 18 provide a constant voltage source for energizing the heater elements 10 and 11 respectively of the tubes 64 and the control tube 18,

T e e of the 'cathodes in the gization of the heater elements 10 and 11 in the manner noted is of great importance since it insuresa substantially constant electron emissivity tubes in question and hence a high degree of stability of the regulatory system. The resistor 15 is used to obtain the desired voltage drop across the constant voltage branch 53-21. A voltmeter 19 connected across the constant voltage branch indicates by a substantially constant reading that the system is operating as desired. The total current in the constant current branch fiowing away from the junction point 53 is designated 13.

In accordance with the present invention, the current I: in the branch 53-41 is maintained substantially constant attending a limited variation in the .voltage of the fluctuating sourc of direct current electromotive force. This achieved by causing a substantially equal but opposite current change in the second parallel branch simultaneously with and in response to a current change in the first parallel branch. Thus, before any current change takes place in the first parallel branch, an application of Kirchhoff's first law relating to networks at the Junetion point 53 gives the following equation:

I1+I2=I3 Eq. (1)

After an incremental change of current AI1 in the first parallel branch attending a voltage fluctuation in the source of direct current electromotive force, the equation now applicable at the junction point 53 will be since as postulated the accompanying incremental change in current of the second parallel branch, namely, AI: must at all times be equal in magnitude to AIl but opposite in sign. Thus, the current I: in the branch 53-21 and hence the voltage thereacross is maintained substantially constant within a limited range of voltage variation of the fluctuating source of direct current electromotive force, as nearly indicated in Fig. 4 of the drawings.

While the voltage across branch 53 -21 is maintained substantially constant since the current therethrough and the equivalent resistance thereof are constant, the voltage across the series resistor in the first parallel branch will vary attending any fluctuation of the current therein, This voltage variation across the resistor 60 occasioned by a' current change in the first parallel branch provides the excitation for the control tube 18 of the voltage amplifier through which the proper voltages are applied to the grids 12 of the tubes N to cause a substantially equal but opposite current change in the second parallel branch. Thus, the desired regulation is achieved.

Proceeding now to a description of the voltage amplifier, I have shown, by way of example, a control tube 18 of the pentode type including an anode 80, cathode 8|, control grid 82, screen grid 83 and suppressor grid 84 which latter grid is tied back to the cathode and both to one of the heater terminals at 85 in the conventional fashion. While a pentode tube such as an RCA Type 6J7 may advantageously be employed in the voltage amplifier because of its high amplification factor, I wish to emphasize in this connection that any conventional prior art triode may be used instead. A high amplification factor makes possible a low voltage excitation and hence a small value for the series resistor 60 in the first parallel branch. Hence, it may be said that the higher th amplification factor of the tube 18, the smaller may be the magnitude'of the series resistor 68. In some instances, where this is desirable, the resistor 80 may even be omitted. Where omitted, however, the regulation will not be as critical as that depicted in Fig. 4 of the drawings but will be a vast improvement over that obtainable with a ballast tube alone.

A high ohmic resistor 89, which draws negligible current, is connected to a suitable point 81 along the series resistor 60 and to the cathode heater terminal 85 in the manner shown to form a potentiometer so that any desired portion of the variable voltage across the resistor 68 may be made available for excitation purposes in the grid circuit of the control tube I8. A slidin contact 88 engages the potentiometer resistor 88 and is secured to a suitable source of biasin voltage 89 for the control grid 82. This biasing voltage 89 is of such a value as to maintain the control grid 82 in its voltage excursions at all times negative with respect to the cathode 8I so as to insure substantially distortionless amplification and the preservation-of the desired voltage relationships within the system.

A load resistor 90 of suitable value has one terminal 9I connected to the anode 80 of the tube 18 and to the grids I2 of the tubes 68 while the remaining terminal 92 thereof is connected to the screen grid 83 of the tube 18 and to a suitable point 93 along the series resistor 00. Thus, the grid circuit of each of the tubes 54 extends from the junction point 53 through the series resistor 60 to the junction point 98 and from thence by means of the conductor 94 to the terminal 92 of the load resistor 90; and from the remaining terminal 9| of this resistor through the conductor 95 to the grids 12 from whence the circuit is completed through the cathodes 69 and the conductor II to the initial junction point 53. The point 93 of the series resistor 60 to which the conductor 94 is secured is preferably chosen to givethe best value of plate potential for the control tube 18. To have raised the plate potential of this tube excessively would have resulted in raising the mean potentials of the grids I2 oi. the tubes 88 to a point where a prohibitive positive grid swing might ensue under certain operating conditions. On the other hand, to have excessively lowered the plate potential of the tube 18 would have needlessly reduced the amplification of the voltage amplifier.

In operation, the main control switch 63 of the regulatory system is closed and the sliding contact 88 of the potentiometer is adjusted until the voltmeter I9 records a substantially constant voltage attending any fluctuation in the voltage posite in sign to All, thus maintaining the constancy of I: in the branch 53-21 all in a manner pointed out hereinbefore.

More specifically, an increase of current A11 in the first parallel branch will cause the grid 82 of the control tube 18 to become less negative by a certain amount with respect to its cathode 8|. This causes an increase in plate current through the tube I8 and hence an increase in voltage drop through the load resistor 90. Since, however, the control grids 12 of the tubes 84 are connected to the terminal 9| of the load resistor 90 by means of the conductor 95, this increase in voltage drop has the effect of causing these grids to become more negative with respect to their cathodes 89. The swing of the individual grids 12, however, is only great enough to cause a decrease of AI: in the total current of the second parallel branch equal to the increase of A11 in the total current of the first parallel branch. Thus, the desired regulation is achieved. That a decrease in current in the first parallel branch will through the voltage drop in the series resistor 50, the associated control tube 18 and load resistor 90 cause an increase in current of the same magnitude in the second parallel branch is believed to be evident.

It is desirable that provision be made for energizing the cathode I3 of the space discharge de- -vice II only after the regulatory system has attained stability so as to avoid any possible impairment of the cathode due to excessive current energization. While this may be achieved manually bysimply shorting out the cathode for a predetermined time through suitable circuit connections, I have devised means for automatically achieving the foregoing. A switch 96 under the control of the solenoid 91 is maintained in a closed position when the solenoid is deenergized by means of a spring 98; and in its-closed position, by virtue of its connection to the cathode energizing conductors 31 and I3 through the conductors 99 and I00 respectively, short circuits the cathode I3 thus preventing any passage oi current therethrough. Any convenient means may be employed for energizing the solenoid 91 when the regulatory system has attained stability, which in consequence of the energization has the effect of opening the switch 98 and thus permitting current flow through the cathode I8 of the space discharge device II so long as the.

main control switch 63 of the regulatory system of the direct current source of electromotive force. current and voltage regulation in the branch 53-21 of the system is obtained. That this is so should be evident from the following discussion.

By adjustment of the sliding contact 88 of the potentiometer in the manner above noted, the needed portion of the variable voltage across the series resistor 80 of the first parallel branch attending any current change therein selected. This incremental change in voltage provides the excitation for the control grid 82 of the tube 18 and in amplified form appears across the load resistor 90. This amplified incremental voltage is of such a value as to change the voltage applied to the grids I2 of the tubes 64 in a manner such that A12 will be equal in magnitude but op- Under these circumstances, the desired is closed.

I have illustrated, by way of example, an instrumentality identified in general by the reference character IOI for achieving the desired energization of the solenoid 91. This instrumentality is connected across the source 01' direct current electromotive force by means of the conductors I02 and I03 in the manner shown and is set in operation by the closure of the main circuit switch 58. In its initial and unenergized state, the movable contact I04 of the current bow I05 engages the fixed current contact I05; and the movable solenoid contact I01. is in engagement with the fixed contact I08 of the heating resistor I09 cooperating with current bow I05. Upon closure of the switch 83, a heating circuit is completed from the positive terminal of the source of electromotive force through the conductors I03 and H0 to the movable solenoid contact I01 and from thence through the fixed contact I08, heating resistor I09 and conductor I02 to the negative terminal of the voltage source. Immediately upon closure of This heating circuit, the movable contact I04, due to the heating of the current bow I05, disengages the fixed contact I and slowly moves to the right for subsequent engagement with the fixed contact II-I.

The engagement of the movable contact I04 with the fixed contact III completes a circuit through the solenoid IIZ which extends from the positive terminal of the source of electromotive force through the conductor I03, current bow I05, solenoid H2 and conductor I02 to the negative source terminal with the result that the movable solenoid contact I01 is moved from engagement with its fixed contact I08 to cause an interruption of the heating circuit heretofore described and into engagement with a second fixed contact II3. By engagement of the movable solenoid contact I01 with the contact II3, a holding circuit for the movable contact I01 is completed from the positive terminal of the source of electromotive force through the conductors I03 and H0 to the movable contact I01 and from thence through the fixed contact II3, solenoid H2 and conductor I02 to the other terminal of the voltage source. This holding circuit is maintained so long as the main control switch 63 is closed.

As the heating circuit hereinbefore described has now been interrupted, the movable contact 04 of the current bow I05 gradually moves from engagement with its fixed contact III back toward the fixed contact I06. Upon engagement with the fixed contact I06 the energizing circuit for the solenoid 91 is completed. This circuit extends from the positive terminal of the source of electromotive force through the conductors I03, IIO, movable solenoid contact I01 and fixed contact II3 to one side of the current bow I05. The circuit continues through the current bow I05, movable contact I04, fixed contact I06, and conductor Ill to one side of the solenoid 91 and from thence through the solenoid and conductor I00 to the conductor 13 which is connected to the negative and remaining terminal of the voltage source.

Thus, after a predetermined time interval has elapsed subsequent to the" closure of the main control switch 63, the solenoid 31 is energized. The regulatory system having by this time attained stability, the energization of the solenoid 91 causes an opening of the switch 96 with the result that the cathode I3 of the space discharge device II is now energized. The time delay in the energization of the cathode is entirely automatic and energization occurs only after the regulatory system has attained stability so that any possibility of damage to the cathode is efoperation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically illustrated and described.

The invention herein described and claimed may be used and manufactured by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What I claim is:

'1. In a regulatory system, a fluctuating source of direct current electromotive force, a first resister, a second resistor and a ballast resistor connected in series relation with the aforesaid source of electromotive force, at least one space discharge device including an anode, cathode and grid connected in parallel with said ballast resistor and said first mentioned resistor to thus form two parallel branches in the regulatory system, a second space discharge device for control purposes and including an anode, cathode and grid, the grid of said second mentioned device being electrically connected to a point on the first mentioned resistor and being at all times maintained at a negative potential with respect to its cooperating cathode, a load resistor in circuit with said second mentioned device, the grid of said first mentioned device being connected to the anode of said second mentioned device and being at all times maintained at a negative potential with respect to its cooperating cathode. the two parallel branches being so arranged that any'change in current in one branch attending any fluctuation in the electromotive force acts through the voltage drop in the first mentioned resistor, the associated control device and load resistor to cause a substantially equal but opposite change in current through the other parallel branch, whereby the current in the second mentioned resistor is maintained substantially constant,

2. In a regulatory system, a fluctuating source of direct current electromotive force, a resistor and a plurality of parallel branches connected in circuit with the aforesaid source of electromotive force, one of said parallel branches including a ballast resistor and the other of said parallel branches including at least one space discharge device incorporating an anode, cathode and grid, and means responsive to any current change in one parallel branch attending any fluctuation in the said electromotive force for causing a substantially equal but opposite current change in the other parallel branch by controlling the grid of the space discharge device therein, whereby the current in the first mentioned resistor is controlled as desired.

3. In a regulatory system, a fluctuating source of direct current electromotive force, a plurality of parallel branches and a branch across which it is desired to control the voltag drop connected in circuit with the aforesaid source of electromotive force, one of said parallel branches including a ballast resistor and the other of said parallel branches including at least one space discharge device-incorporating an anode, cathode and grid, and means responsive to any current change in the parallel branch including the ballast resistor for causing a substantially equal but opposite current change in the other parallel branch by controlling the grid of the space discharge device therein whereby the voltage drop across the remaining circuit branch is controlled a desired.

4. In'a regulatory system, a fluctuating source of direct current electromotive force, a resistor and a plurality of parallel branches connected in circuit with the aforesaid source of electromotive force, one of said parallel branches including a ballast resistor and a resistor in series therewith and the other of said parallel branche including at least one space discharge device incorporating an anode, cathode and grid, and means responsive to any current change in one parallel branch attending any fluctuation in the said electromotive force for causing a substantially equal but opposite current change in the other parallel branch, whereby the current in the first mentioned resistor is maintained substantially constant, the said means being electrically connected to the series resistor in one of the parallel branches and to the grid of. the space discharge device in the other of said branches.

5. In a regulatory system, a fluctuating source of direct current electromotive force, a plurality of parallel branches and a branch across which it is desired to maintain a substantially constant stant, the said means being electrically connected to the serie resistor in one of the parallel branches and to the grid of the space discharge device in the other or said parallel branches.

6. In a regulatory system, a fluctuating source of direct current electromotiv force, a resistor and a plurality of parallel branches connected in circuit with the aforesaid source of electromotive force, one of said parallel branches including a ballast resistor and a resistor in series therewith and'the other of said parallel branches including at least one space discharge device incorporating an anode, cathode and grid, and means responsive to any current change in one parallel branch attending any fluctuation in the said electromotive force for causing a substantially equal but opposite current change in the other parallel branch, whereby the current in the first mentioned resistor i maintained substantially constant, the said means including a secand space discharge device incorporating an anode, cathode and grid, the grid of said second mentioned device being electrically connected to a point on'the' series resistor and being at all times maintained at a negative potential with respect to its cooperating cathode and the grid of said first mentioned device being connected to the anode of said second mentioned device and being also atall times maintained at a negative potential with respect to its cooperating cathode.

7. In a regulatory system, a fluctuating source of direct current electromotive force, a plurality of parallel branches and a branch'across which it is desired to maintain a substantially constant voltage drop connected in circuit with the aforesaid source of electromotive force, one of said parallel branches including a ballast resistor and a resistor in series therewith and the other of said parallel branches including at least one space discharge device incorporating an anode, cathode and grid, and means responsive to any current change in one parallel branch attending any fluctuation in the said electromotive force 'for causing a substantially equal but opposite current change in the other parallel branch, whereby the voltage drop across the remaining circuit branch is maintained substantially constant, the said means including a second space discharge device incorporating an anode, cathode and grid, the grid of said second mentioned device being electrically connected to a point on the series resistor and being at all times maintained at a negative potential with respect to its cooperating cathode and the grid of said first mentioned device being connected to the anode of said second mentioned device and being also at all times maintained at a negative potential with respect to its cooperating cathode.

8. In a regulatory system, a fluctuating source of direct current electromotive force, a plurality of parallel branches and a branch across which it, is desired to maintain a substantially constant voltage drop connected in circuit with the aforesaid source of electromotive force, one of said parallel branches including a ballast resistor and a resistor in series therewith and the other of said parallel branches including at least one space discharge device incorporating an anode, cathode and grid, and means responsive to any current change in one parallel branch attending any fluctuation in the said electromotive force for causing a substantially equal but opposite current change in the other parallel branch,-

operating cathode and the grid of said first mentioned device being connected to the anode of said second mentioned device and' being also at all times maintained at a negative potential with respect to its cooperating cathode.

9. In a regulatory system, a fluctuating source of direct current electromotive force, a plurality of parallel branches anda branch across which it is desired to control the voltage drop connected in circuit with the aforesaid source 0! electromotive force, one of said parallel branches including a ballast resistor, and means responsive to any current change in the parallel branch including the ballast resistor for causing a substantially equal but opposite current change in the other parallel branch, whereby the voltage drop across the remaining circuit branch is con-- trolled as desired.

WAYNE C. HALL. 

